The present invention relates to systems and methods for aerodynamic flow, and more particularly to an enhanced performance air moving assembly and the components thereof.
Air moving devices such as fans and blowers are an important aspect of cooling systems, such as the cooling systems employed in today""s electronic devices (e.g., computer devices such as central processing units (CPUs), storage devices, server devices, video cards). In the case of electronic devices, such air moving devices are typically used to push and/or draw air across heat sinks, as well as to remove waste heat from components of the electronic devices. Moreover, in addition to developing airflow through an electronic device, the fans, blowers, etc., must overcome system back pressure, which is the pressure lost due to aerodynamic resistance at the device. System back pressure depends upon such things as the number of heat sinks in the device, as well as the number of other components in the device.
Reliability is desired for the fans, blowers, etc., employed in the above mentioned cooling applications, especially for high end electronic devices, because when one fan fails, typically the remaining fans are unable to provide enough flow to compensate for the non-functioning fan. Unfortunately, these fans, etc., have high failure rates, most often on account of bearing failures. For this reason, most system designers employ N+1 fan configurations to compensate for the failure of a single fan. Examples of N+1 system designs are illustrated in FIGS. 1A and 1B.
N+1 configurations have two expected benefits. First, in N+1 configurations, if one fan fails, a redundant fan continues to push air through the system, thereby increasing the reliability of the cooling system. Secondly, for N+1 series configurations, particularly the configuration of FIG. 1B, if both the N and +1 fans are operating, theoretically, double the pressure should be provided by the two fans in series compared to that provided by a single fan (assuming the pressures are additive).
However, rarely, if ever, does the second expected benefit occur. One reason for this is that airflow exiting the first fan normally has some xe2x80x9cswirlxe2x80x9d, meaning that the velocity of the airflow has a rotational component, as well as an axial component. This phenomena is illustrated in FIG. 2. As can be seen in FIG. 2, airflow entering fan 210 has a velocity represented in FIG. 2 by velocity vector 200. After passing through fan 210, velocity vector 200 develops both an axial component 220 and a rotational component 230. The swirl provided by first fan 210 normally degrades the performance of second fan 240. One reason for this is that typically the airflow exiting first fan 210 is swirling in the same direction as the rotation of the blades of second fan 240. As a result, the rotational speed of the blades of second fan 240 is effectively decreased.
In addition to the above, N+1 configurations have other notable disadvantages, to include the significant space required to implement N+1 configurations. Oftentimes, a desired design for an electronic device and/or cooling system does not leave adequate space for an N+1 configuration. As a result, cooling system designs and/or electronic device designs must be compromised to accommodate an N+1 configuration.
Another disadvantage of prior art air moving assemblies are losses due to the expansion and contraction of airflow as air passes through the assemblies.
Also included among the disadvantages of N+1 configurations is the fact that if one fan fails, the non-functioning fan creates a large impedance (i.e., airflow obstruction) in the cooling system. Therefore, two fans in series with one fan not working is worse for the cooling system then one fan by itself.
Another undesirable side effect of N+1 configurations is unwanted noise, to include acoustic beat frequencies.
The present invention is directed to an enhanced performance air moving assembly. In one embodiment, the air moving assembly includes a first air moving device (e.g., a fan, a blower) and a stator, the stator being operable to at least reduce one expansion and/or one contraction of airflow passing through the assembly. Preferably, the stator is also operable to impart to or adjust swirl for airflow passing through said stator. In at least one embodiment, the stator imparts or adjusts a certain swirl such that upon exiting the air moving assembly, the airflow has little or no swirl. Furthermore, various embodiments of the air moving assembly of the present invention include more than one air moving device and/or more than one stator. In at least one embodiment, the air moving assembly of the present invention is employed in cooling applications for electronic devices.
Moreover, in at least one embodiment, the air moving assembly includes a first air moving apparatus, as well as a second air moving apparatus, coupled to a strut assembly. In at least one of these embodiments, the strut assembly includes a stator operable to reverse the direction of swirl of the airflow exiting the first air moving apparatus.
It should be recognized that one technical advantage of one aspect of at least one embodiment of the present invention is that undesirable swirl normally hampering the efficiency of prior art air moving devices is counteracted, resulting in a higher performance air moving device. In addition, certain losses experienced in prior art systems, such as expansion and contraction losses, are reduced (and in some instances, eliminated) in various embodiments of the present invention. Moreover, in at least one embodiment of the present invention, valuable device space is saved by the sharing of components between air moving devices (e.g., shared strut assembly). Furthermore, in at least one embodiment, the air moving assembly of the present invention helps compensate for, at least in part, the impedance resulting from a non-functioning fan (i.e., the failed fan state). In addition, in at least one embodiment, acoustic beat frequencies are limited by the present invention.